Mutation Size Optimizes Speciation In An Evolutionary Model,
2010
University of Missouri
Mutation Size Optimizes Speciation In An Evolutionary Model, Nathan Dees, Sonya Bahar
Physics Faculty Works
The role of mutation rate in optimizing key features of evolutionary dynamics has recently been investigated in various computational models. Here, we address the related question of how maximum mutation size affects the formation of species in a simple computational evolutionary model. We find that the number of species is maximized for intermediate values of a mutation size parameter μ; the result is observed for evolving organisms on a randomly changing landscape as well as in a version of the model where negative feedback exists between the local population size and the fitness provided by the landscape. The same result …
How Lightning Tortuosity Affects The Electromagnetic Fields By Augmenting Their Effective Distance,
2010
Trinity University
How Lightning Tortuosity Affects The Electromagnetic Fields By Augmenting Their Effective Distance, S L. Meredith, S K. Earles, I N. Kostanic, Niescja E. Turner, C E. Otero
Physics and Astronomy Faculty Research
A novel approach for developing the electromagnetic fields from a lightning return stroke which follows a tortuous path will be presented. The proposed model is unique in that it recognizes that the symmetrical tortuosity of lightning directly impacts the observable distance r, which in turn, alters the resulting electromagnetic fields. In the literature, lightning return stroke models typically employ the assumption that the cloud-to-ground path is straight. Although this assumption yields fairly consistent results across an array of varying approaches, it does not account for lightning's natural physical appearance. Furthermore, straight-line models only account for the cloud-to-ground discharges and do …
Spectroscopic Abundances And Membership In The Wolf 630 Moving Group,
2010
University of Rochester
Spectroscopic Abundances And Membership In The Wolf 630 Moving Group, Eric J. Bubar, Jeremy R. King
Publications
The concept of kinematic assemblages evolving from dispersed stellar clusters has remained contentious since Eggen’s initial formulation of moving groups in the 1960s. With high-quality parallaxes from the Hipparcos space astrometry mission, distance measurements for thousands of nearby, seemingly isolated stars are currently available. With these distances, a high-resolution spectroscopic abundance analysis can be brought to bear on the alleged members of these moving groups. If a structure is a relic of an open cluster, the members can be expected to be monolithic in age and abundance in as much as homogeneity is observed in young open clusters. In this …
Locating The Accretion Footprint On A Herbig Ae Star: Mwc 480,
2010
Eureka Scientific
Locating The Accretion Footprint On A Herbig Ae Star: Mwc 480, C A. Grady, K Hamaguchi, G Schneider, B Stecklum, B E. Woodgate, J E. Mccleary, G M. Williger, M L. Sitko, F Menard, Th. Henning, Sean D. Brittain
Publications
Accretion is a fundamental process which establishes the dynamics of the protoplanetary disk and the final properties of the forming star. In solar-type stars, the star–disk coupling is determined by the magnetic field structure, which is responsible for funneling material from the disk midplane to higher latitudes on the star. Here, we use pan-chromatic data for the Herbig Ae star MWC 480 to address whether similar processes occur in intermediatemass stars. MWC 480 has X-ray emission typical of actively accreting Herbig Ae stars, but with ∼10× more photoelectric absorption than expected from optical and FUV data. We consider three sources …
Swift Monitoring Of Cygnus X-2: Investigating The Near-Ultraviolet-X-Ray Connection,
2010
University of California at Santa Barbara
Swift Monitoring Of Cygnus X-2: Investigating The Near-Ultraviolet-X-Ray Connection, E. S. Rykoff, E. M. Cackett, J. M. Miller
Physics and Astronomy Faculty Research Publications
The neutron star X-ray binary (NSXRB) Cyg X-2 was observed by the Swift satellite 51 times over a 4 month period in 2008 with the X-ray Telescope (XRT), UV/optical telescope, and Burst Alert Telescope (BAT) instruments. During this campaign, we observed Cyg X-2 in all three branches of the Z track (horizontal, normal, and flaring branches). We find that the NUV emission is uncorrelated with the soft X-ray flux detected with the XRT and is anticorrelated with the BAT X-ray flux and the hard X-ray color. The observed anticorrelation is inconsistent with simple models of reprocessing as the source of …
On Using The Color-Magnitude Diagram Morphology Of M67 To Test Solar Abundances,
2010
Max Planck Institute for Astrophysics
On Using The Color-Magnitude Diagram Morphology Of M67 To Test Solar Abundances, Z. Magic, A. Serenelli, A. Weiss, B. Chaboyer
Dartmouth Scholarship
The open cluster M67 has solar metallicity and an age of about 4 Gyr. The turnoff (TO) mass is close to the minimum mass for which solar metallicity stars develop a convective core during main sequence evolution as a result of the development of hydrogen burning through the CNO cycle. The morphology of the color-magnitude diagram (CMD) of M67 around the TO shows a clear hook-like feature, a direct sign that stars close to the TO have convective cores. VandenBerg et al. investigated the possibility of using the morphology of the M67 TO to put constraints on the solar metallicity, …
Observing Co In Circumstellar Disks,
2010
Clemson University
Observing Co In Circumstellar Disks, Matthew Troutman
All Dissertations
This dissertation includes high-resolution, near-infrared spectroscopy to study CO in circumstellar disks around Herbig Ae/Be stars. The velocity-resolved spectra was used to measure the distribution of gas in the circumstellar disk and thus determine the evolutionary state of the system. Near-infrared spectra were obtained on over 30 young circumstellar disks around Herbig Ae/Be stars to study the physical processes in the disk. The radial location of the CO emitting gas bears directly on the evolutionary state of the transition objects in the sample. This study included a detailed study of the debris disk star β Pictoris where the disk mass …
Internal Transitions In Nuclei And Applications To Astrophysics And Cosmochemistry,
2010
Clemson University
Internal Transitions In Nuclei And Applications To Astrophysics And Cosmochemistry, Joseph Johnson
All Dissertations
In this dissertation I analyze internal transitions in nuclei and their potential effects on s-process branching and on accelerated β-decay in cosmochemical samples. To accomplish my analysis, I have constructed a number of computational tools, which I have publicly released or make available through this thesis. I apply my analysis to the question of s-process branching at 186Re and study the implications for the osmium isotopes in mainstream presolar SiC grains. My essential conclusion is that the problem of the large neutron flux inferred from the SiC osmium isotopic abundances cannot be solved by branching through an out-of-equilibrium isomer of …
Dark Matter Halos And Evolution Of Bars In Disk Galaxies: Varying Gas Fraction And Gas Spatial Resolution,
2010
Georgia Southern University
Dark Matter Halos And Evolution Of Bars In Disk Galaxies: Varying Gas Fraction And Gas Spatial Resolution, Jorge Villa-Vargas, Isaac Shlosman, Clayton Heller
Physics & Astronomy: Faculty Publications
We conduct numerical experiments by evolving gaseous/stellar disks embedded in live dark matter halos aiming at quantifying the effect of gas spatial resolution and gas content on the bar evolution. Three model sequences have been constructed using different resolutions, and the gas fraction has been varied along each sequence within the range of f g = 0%-50%, but keeping the disk and halo properties unchanged. We find that the spatial resolution becomes important with an increase in the gas content. For the higher resolution model sequences, we observe a bimodal behavior in the bar evolution with respect to the gas …
Plans For The First Balloon Flight Of The Gamma-Ray Polarimeter Experiment (Grape),
2010
University of New Hampshire - Manchester
Plans For The First Balloon Flight Of The Gamma-Ray Polarimeter Experiment (Grape), Taylor Connor, Chris Bancroft, Peter F. Bloser, Jason S. Legere, Mark L. Mcconnell, James M. Ryan
Space Science Center
We have developed a design for a hard X-ray polarimeter operating in the energy range from 50 to 500 keV. This modular design, known as GRAPE (Gamma-Ray Polarimeter Experiment), has been successfully demonstrated in the lab using partially polarized gamma-ray sources and using fully polarized photon beams at Argonne National Laboratory. In June of 2007, a GRAPE engineering model, consisting of a single detector module, was flown on a high altitude balloon flight to further demonstrate the design and to collect background data. We are currently preparing a much larger balloon payload for a flight in the fall of 2011. …
Development Of The Advance Energetic Pair Telescope (Adept) For Medium-Energy Gamma-Ray Astronomy,
2010
NASA Goddard Space Flight Ctr
Development Of The Advance Energetic Pair Telescope (Adept) For Medium-Energy Gamma-Ray Astronomy, Stanley D. Hunter, Peter F. Bloser, Michael P. Dion, Mark L. Mcconnell, Georgia A. Denolfo, Seunghee Son, James M. Ryan, Floyd Stecker
Space Science Center
Progress in high-energy gamma-ray science has been dramatic since the launch of INTEGRAL, AGILE and FERMI. These instruments, however, are not optimized for observations in the medium-energy (~0.3< Eγ < ~200 MeV) regime where many astrophysical objects exhibit unique, transitory behavior, such as spectral breaks, bursts, and flares. We outline some of the major science goals of a medium-energy mission. These science goals are best achieved with a combination of two telescopes, a Compton telescope and a pair telescope, optimized to provide significant improvements in angular resolution and sensitivity. In this paper we describe the design of the Advanced Energetic Pair Telescope (AdEPT) based on the Three-Dimensional Track Imager (3-DTI) detector. This technology achieves excellent, mediumenergy sensitivity, angular resolution near the kinematic limit, and gamma-ray polarization sensitivity, by high resolution 3-D electron tracking. We describe the performance of a 30×30×30 cm3 prototype of the AdEPT instrument.
A Fast Scintillator Compton Telescope For Medium-Energy Gamma-Ray Astronomy,
2010
University of New Hampshire
A Fast Scintillator Compton Telescope For Medium-Energy Gamma-Ray Astronomy, Peter F. Bloser, James M. Ryan, Jason S. Legere, Manuel Julien, Chris Bancroft, Mark L. Mcconnell, Mark Wallace, R M. Kippen, Shawn Tornga
Space Science Center
The field of medium-energy gamma-ray astronomy urgently needs a new mission to build on the success of the COMPTEL instrument on the Compton Gamma Ray Observatory. This mission must achieve sensitivity significantly greater than that of COMPTEL in order to advance the science of relativistic particle accelerators, nuclear astrophysics, and diffuse backgrounds, and bridge the gap between current and future hard X-ray missions and the high-energy Fermi mission. Such an increase in sensitivity can only come about via a dramatic decrease in the instrumental background. We are currently developing a concept for a low-background Compton telescope that employs modern scintillator …
Discovery Of Very High Energy Gamma-Ray Emission From The Snr G54.1+0.3,
2010
Department of Physical Sciences, Cork Institute of Technology, Bishopstown, Cork, Ireland
Discovery Of Very High Energy Gamma-Ray Emission From The Snr G54.1+0.3, P. T. Reynolds, Et Al
Physical Sciences Publications
We report the discovery of very high energy (VHE) gamma-ray emission from the direction of the SNR G54.1+0.3 using the VERITAS ground-based gamma-ray observatory. The TeV signal has an overall significance of 6.8σ and appears pointlike given the resolution of the instrument. The integral flux above 1 TeV is 2.5% of the Crab Nebula flux and significant emission is measured between 250 GeV and 4 TeV, well described by a power-law energy spectrum dN/dE ~ E –Γ with a photon index Γ = 2.39 ± 0.23stat ± 0.30sys. We find no evidence of time variability among observations …
The First Vlbi Image Of The Young, Oxygen-Rich Supernova Remnant In Ngc 4449,
2010
York
The First Vlbi Image Of The Young, Oxygen-Rich Supernova Remnant In Ngc 4449, M. F. Bietenholz, N. Bartel, D. Milisavljevic, R. A. Fesen
Dartmouth Scholarship
We report on sensitive 1.4-GHz VLBI radio observations of the unusually luminous supernova remnant SNR 4449-1 in the galaxy NGC 4449, which gave us the first well-resolved image of this object. The remnant's radio morphology consists of two approximately parallel bright ridges, suggesting similarities to the barrel shape seen for many older Galactic supernova remnants or possibly to SN 1987A. The angular extent of the remnant is 65 × 40 mas, corresponding to (3.7 × 2.3) × 1018 (D/3.8 Mpc) cm. We also present a new, high signal-to-noise ratio optical spectrum. By comparing the remnant's linear size …
Sn 2010u: A Luminous Nova In Ngc 4214,
2010
University of Minnesota
Sn 2010u: A Luminous Nova In Ngc 4214, Roberta M. Humphreys, José L. Prieto, Philip Rosenfield, L. Andrew Helton, Christopher S. Kochanek, K. Z. Stanek, Rubab Khan, Dorota Szczygiel, Karen Mogren, Robert A. Fesen
Dartmouth Scholarship
The luminosity, light curve, post-maximum spectrum, and lack of a progenitor on deep pre-outburst images suggest that SN 2010U was a luminous, fast nova. Its outburst magnitude is consistent with that for a fast nova using the maximum magnitude-rate of decline relationship for classical novae.
Observation And Analysis Of The Hydrogen 21-Cm Line Using A Small Radio Telescope,
2010
University of Alabama in Huntsville
Observation And Analysis Of The Hydrogen 21-Cm Line Using A Small Radio Telescope, Lisa Friederich
Honors Capstone Projects and Theses
No abstract provided.
The Cosmos Out Your Back Door,
2010
Utah State University
Prediction And Study Of Binary Alloys Using First-Principles Methods,
2010
Brigham Young University - Provo
Prediction And Study Of Binary Alloys Using First-Principles Methods, Richard Hansen Taylor Ii
Theses and Dissertations
The utility of first-principles methods in the study and prediction of binary alloys is showcased by three detailed studies. In particular, the T = 0K cluster expansion methodology in conjunction with finite temperature statistical modeling by a Monte Carlo method is used to study two systems of practical interest, Mg-Li (magnesium-lithium) and Rh-W (rhodium-tungsten). Also, an empirically-informed, high-throughput approach to crystal structure prediction is shown by a study of the Pt$_8$Ti (the Pietrokowsky phase) phase and a broad and detailed analysis of binary Mg-X phases in 39 systems (X=Ag, Al, Au, Ca, Cd, Cu, Fe, Ga, Ge, Hf, Hg, In, …
Charged, Rotating Black Holes In Higher Dimensions,
2010
Brigham Young University - Provo
Charged, Rotating Black Holes In Higher Dimensions, Christopher Bruce Verhaaren
Theses and Dissertations
We present a method for solving the Einstein-Maxwell equations in a five dimensional, asymptotically flat, black hole spacetime with three commuting Killing vector fields. In particular, we show that by reducing the dimension of the Einstein-Maxwell equations in a Kaluza-Klein like manner we can determine the components of the metric and vector potential which lie in the direction of the Killing vector fields. These components are determined by nine scalar fields each of which satisfy a partial differential equation in two variables. These equations take the form of an elliptic operator set equal to a nonlinear source. We find evidence …
A Mass-Loss Rate Determination For Zeta Puppis From The Quantitative Analysis Of X-Ray Emission-Line Profiles,
2010
Swarthmore College
A Mass-Loss Rate Determination For Zeta Puppis From The Quantitative Analysis Of X-Ray Emission-Line Profiles, David H. Cohen, M. A. Leutenegger, Emma Edwina Wollman , '09, J. Zsargó, D. J. Hillier, R. H.D. Townsend, S. P. Owocki
Physics & Astronomy Faculty Works
We fit every emission line in the high-resolution Chandra grating spectrum of. Pup with an empirical line profile model that accounts for the effects of Doppler broadening and attenuation by the bulk wind. For each of 16 lines or line complexes that can be reliably measured, we determine a best-fitting fiducial optical depth, tau(*) equivalent to kappa(M) over dot/4 pi R(*)upsilon(infinity), and place confidence limits on this parameter. These 16 lines include seven that have not previously been reported on in the literature. The extended wavelength range of these lines allows us to infer, for the first time, a clear …
